Hot-gas reciprocating engine and control device

ABSTRACT

A hot-gas reciprocating engine of which the working space communicates via two communication ducts with a storage container for working medium, with a compressor and a controllable valve present in one communication duct, the compressor inlet communicating with the storage container and the compressor outlet with the working space, the valve being present between the storage container and the compressor inlet.

I v United States Patent 1 91 1111 3,886,743 Abrahams 1 June 3, 1975 HOT-GAS RECIPROCATING ENGINE AND [56] References Cited CONTROL DEVICE UNITED STATES PATENTS [75] Inventor: Jacobus Huhertus Abrahams, 2157.229 5/l939 Bush 60/521 E nmasingcl Eindhoyen 2583.311 Van HCCCkCI'Cl'I 1 Netherlands 2.992.536 7/1961 Carnahan 60 521 l l Assigneci Philips Corporation, Ncw Primary ExaminerMartin P. Schwadron Ymke Assistant E.\'aminerH. Burks 22 Filed; 23 1973 Attorney, Agent, or Firm-Frank R. Trifari [21] Appl. No.: 418,297 57 ABSTRACT Related US. Application Data A hot-gas reciprocating engine of which the working [63] Continuation Of Ser. N6. 307.998. NOV. 20. 1972. spilce Communicate? via two Communication ducts w1th a storage container for working medium, with a [30] Foreign Application priority Data compressor and a controllable valve present in one Dec 2 1971 Netherlands 7116550 communication duct, the compressor inlet communieating with the storage container and the compressor [52] us CL 60/521 outlet with the working space, the valve being present [511 m. C1..Jijijiijijijjjjjjj:57""1111 "163 7/06 between me eeeeeee end the eemeeeeeee [58] Field of Search 7. 60/521, 524

4 Claims, 5 Drawing Figures Patented June 3, 1975 3,886,743

5 Sheets-Sheet 1 Fig.1

Patented June 3, 1975 3,886,743

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Patented June 3, 1975 5 Sheets-Sheet 5 ooo o Q o o HOT-GAS REClPROCA'llNG ENGINE AND CONTROL DEVlCE This is a continuation, of application Ser. No. 307,998, filed Nov. 20, 1972.

BACKGROUND OF THE INVENTION Hot-gas reciprocating engine comprising a device for controlling the quantity by weight of working medium present in a working space.

The invention relates to a hot-gas reciprocating engine comprising a device for controlling the quantity by weight of working medium present in a working space of the engine. Such a device comprises a storage container for working medium which communicates with the working space both via a first communication duct in which a first controllable cock and a compressor having an inlet for lower-pressure working medium and an outlet for higher-pressure medium are incorporated and via a second communication duct in which a second controllable cock is incorporated. A hot-gas reciprocating engine of this type is known from the U.S. Pat. No. 3,372,539.

Hot-gas reciprocating engines are to be understood to mean within the scope of the present invention, hotgas piston engines. cold-gas refrigerators and heat pumps. 1n the working space of said machines the working medium is alternately compressed when it is present mainly in a partial space of the working space, the compression space, then transported, via a regenerator, to a partial space, the expansion space, is then expanded, when the working medium is present mainly in the expansion space, and finally transported back via the regenerator to the compression space with which the cycle is completed. The compression and expansion spaces during operation have mutually different average temperatures.

Structurally, said hot-gas reciprocating engines are to be distinguished between hot-gas reciprocating engines of the displacer type (British Pat. No. 1,024,274) and hot-gas reciprocating engines of the two piston type (British Pat. No. 1,053,896).

In hot-gas reciprocating engines of the displacer type, a piston ensures the alternate compression and expansion of the working medium in the working space, while a displacer ensures a transport of the working medium from the compression space to the expansion space and vice versa.

In hot-gas reciprocating engines of the two-piston type, both a compression piston and an expansion piston are present which in cooperation ensure the desired compression, the transport, and the expansion of the working medium.

With the device for controlling the quantity by weight of working medium in the working space of the hot-gas reciprocating engine. the power of said machine can be varied due to a variation of the average working medium pressure level in the working space.

In the hot-gas reciprocating engine known from the U.S. Pat. No. 3,372,539, working medium is withdrawn from the working space via the first communication duct and forced into the storage container by the external compressor present in said duct. So in this case the compressor inlet communicates with the working space and the compressor outlet communicates with the storage container which is constructed as a high-pressure storage container. The first controllable cock is present in the part of the first communication duct present between the working space and the compressor inlet and in the closed position and during normal operation of the engine ensures that working medium is not compressed from the working space to the storage container by the compressor which is also operating then.

Instead of an external compressor, the compressor may also be arranged inside the engine. In that case the internal compressor may form an integral part of the engine as is proposed in Dutch patent application No. 71.06.03). Supply of working medium to the working space from the high-pressure storage container occurs via the second communication duct by opening the second controllable cock present in said duct.

The known hot-gas reciprocating engine with the device for varying the quantity by weight of working medium in the working space has a few drawbacks. Notably, in hot-gas reciprocating engines for traction purposes it may occur in certain circumstances, that the engine cuts out, for example, in the case of a sudden stop of the vehicle, while a high working medium pressure level prevails in the working space of the engine. The compressor coupled to the engine shaft thus also gets out of operation so that working medium can no longer be pumped from the working space to the highpressure storage container.

it is not possible, or at least very difficult, in the case ofa high working medium pressure level in the working space of the engine to get the engine, started then without extra measures. Extra starting measures so as to uncouple the engine, for example, a slipping clutch or a centrifugal clutch, make the engine complicated and expensive and are therefore undesirable. Starting problems may occur also in the case in which after cut-out of the engine a low pressure level prevails in the working space of the engine and the working medium thus is mainly present in the high-pressure storage container. It may occur as a matter of fact that by some leakage of the second controllable cock working medium is communicated from the high-pressure storage container to the working space of the engine. The pressure level in the engine working space in particular in the case ofa long stationary position of the engine, may as a result increase to such an extent that starting of the engine presents great difficulties, or is impossible.

Since working medium should be forced in the storage container under a high pressure, a compressor having a high compression ratio is required. However, with high pressure ratios, high compression temperatures of the working medium occur. In addition, working medium drawn in from the working space by the compressor already has a rather high temperature, which also contributes to a high final compression temperature. All this has an unfavourable influence on the life of the compressor, notably on the life of the seals which usually are manufactured from a synthetic material, and on the life of the inlet and outlet valves.

1n the known engine the further drawback occurs that with the closed position of the first controllable cock incorporated in the part of the first communication duct present between the working space and the compressor inlet, the pressure in the working space of the compressor varies between the pressure in the relevant part of the first communication duct which is very low due to the compressor action and the high pressure in the storage container. In order to reduce said very larger pressure variations, special structural measures are taken (working medium short-circuiting) which, however, make the assembly complicated and more expensive.

SUMMARY OF THE INVENTION It is the object of the present invention to avoid the said above-mentioned drawback. In order to realize this object, the hot-gas reciprocating engine according to the invention is characterized in that the compressor inlet is connected to the storage container. and the compressor outlet is connected to the working space, the first controllable cock being incorporated in the part of the first communication duct present between the storage container and the compressor inlet.

When the pressure level of the working medium in the working space of the engine should be reduced, the second controllable cock in the second communication duct now serving as an outlet duct for the working space, is opened and working medium flows to the storage container. The storage container now is a low pressure storage container. The engine can now easily be started without special precautions at the lowpressure level in the working space.

Supply of working medium to the working space occurs in the present case via the first communication duct. In the open position of the first controllable duct, the compressor pumps working medium from the lowpressure storage container to the working space of the engine. So it is sufficient to have a compressor which has a comparatively low compression ratio. Also due to the drawing-in of a comparatively cold working medium, the occurring compression temperatures of the working medium therefore are also comparatively low which is favorable for the life of the compressor.

In the closed position of the first controllable cock, now incorporated in the part of the first communication duct which is present between the storage container and the compressor inlet, the pressure variations occurring in the compression space of the compressor are small in this case.

The invention will be described in greater detail with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows very diagrammatically the improved control device of a known hot-gas engine,

FIG. 2 is a more structural embodiment of the hotgas engine shown in FIG. 1,

FIGS. 3 to show diagrammatically hot-gas engines which are provided with a buffer space which forms part of one of the communications between the storage container for working medium and the working space of the engine. In addition, in the hot-gas engine shown in FIGS. 4 and 5 the compressor forms an integral part of the engine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Reference numeral 1, in FIG. 1 denotes a working space of a hot-gas engine. and reference numeral 2 denotes a storage container for working medium. The storage container 2 communicates with the working space 1 via a communication duct 3, in which a controllable cock 4 as well as a compressor 5 having an inlet 6 for lower-pressure working medium and an outlet 7 for compressed medium are incorporated.

Storage container 2 also communicates with working space 1 via a second communication duct 8 in which a second controllable cock 9 is incorporated. The compressor 5 communicates with its inlet 6, the suction side, with storage container 2 and with its outlet 7, the compression side, with the working space I, while controllable cock 4 is present between the storage container 2 and the compressor inlet 6.

When the working medium pressure level in the working space I should be reduced, either to enable starting of the engine or to reduce the power supplied during operation by the engine, the cock 9 is opened so that working medium flows from the working space 1 to the storage space 2. When working medium should be supplied to the working space 1 so as to increase the power supplied by the engine, the cock 4 is opened and working medium is drawn in from the storage container 2 by the compressor 5 mid supplied to the working space 1.

Reference numeral 20 in FIG. 2 denotes a cylinder of a hot-gas engine. A piston 21 and a displacer 22 reciprocate in said cylinder with a mutual phase difference. These members are coupled to a driving mechanism not shown. The piston 21 and the lower face of the displacer 22 vary the volume of a compression space 23; the displacer 22 varies with its upper face the volume of an expansion space 24. These two spaces communicate with each other via a cooler 25, a regenerator 26 and a heater 27. A burner 28 supplies thermal energy to the heater 27.

Compression space 23 and expansion space 24 together constitute the working space of the hot-gas engine with which the device for controlling the quantity by weight of working medium in said working space communicates. The same reference numerals are used for these components as for the device shown in FIG. 1, while the operation of the device is as described above.

FIG. 3 shows diagrammatically a hot-gas engine having a control device the various components of which are denoted by the same reference numerals as in FIG. 2. This hot-gas engine comprises a buffer space 30 below the piston 21. The buffer space 30 forms part of the communication duct 3 between the storage container 2 and the working space. A check valve 31 which opens in the direction of the working space is incorporated in the part of the duct 3 present between the buffer space 21 and the working space of the engine.

In the open position of the cock 9, working medium flows from the compression space 23 to the storage container 2. As a result of this the pressure in the working space drops so that check valve 31 opens and working medium flows from the buffer space 30 to the working space and the storage container 2, respectively.

When working medium is supplied from the storage container 2 to the working space of the engine, com pressor 5 draws in working medium and delivers it in buffer space 30 so that the pressure in said space increases. Consequently, the check valve 31 opens so that working medium can flow from the buffer space 30 to the working space. in this case the compression space 23. Of course cock 9 is then closed.

In the hot-gas engines shown in FIGS. 4 and S, the same reference numerals are used for components corresponding to the engine shown in FIG. 3. Both in the hot-gas engine shown in FIG. 4 and in that shown in FIG. 5 the compressor of the control device forms an integral part of the engine present within the buffer space.

Reference numeral in FIG. 4 denotes a cylindrical compressor housing which comprises a compression space 41 for working medium to be compressed. The volume of the compression space 41 is varied by a flange 42 which serves as a compression piston and is secured to the piston rod 43. A piston ring 44 incorporated in a groove in the wall of the compressor housing 40 serves as an inlet valve for the compression space 41. Piston ring 44 comprises radially extending grooves 44' on its upper side so that there is always an open communication between the compression space 41 and the space in groove 45 behind the piston ring 44. The compression space 41 is provided with an outlet valve 46.

During operation of the hot-gas engine. the flange 42 moves with piston rod 43 and piston 21, respectively. When working medium should be conveyed from the storage container 2 to the working space of the engine, the cock 4 is opened. During the upward movement of the piston rod. the upper side of the piston ring 44 provided with radial grooves 44 engages the upper side of groove 45, when the pressure in the compression space 41 is lower than in the communication duct 3. However, no seal is formed so that working medium is drawn in from the storage container 2 into the compression space 41.

After flange 42 has passed its uppermost dead position and moves downwards. the lower side of the piston ring 44 engages the lower side of the groove 45 when the pressure in the compression space 41 becomes larger than in the communication duct 3 and a good seal is formed so that the working medium present in the compression space 41 cannot flow back.

The working medium in the compression space 41 is further compressed and leaves said space via outlet valve 46 in the outlet 7 which opens into buffer space 30. Since the pressure in the buffer space 30 increases, check valve 31 will open so that working medium flows from the buffer space to the working space of the engine.

When the working medium pressure in the working space of the engine is to be reduced so as to be able to start the engine or to reduce the supplied power during operation of the engine. simply cock 9 only need be opened.

ln FIG. 5 the compressor inside the buffer space 30 is formed by a cylindrical housing 50 within which a compression space 51 is present the volume of which is varied by a plunger 52 which is secured to the piston rod 54 via a connection element 53.

The compressor has a normal inlet valve 55 and an outlet valve in the form of a piston ring 56 incorporated in a groove 57 in the wall of plunger 52. Between the upper side of the piston ring 57 and the upper side of the groove 57 a compression spring 58 is present which exerts a downwards force on the piston ring 56.

When the plunger 52 moves upwards. the pressure in the compression space 51 decreases. lnlet valve 55 opens so that in the open position of the cock 4 working medium is drawn in from the storage container 2. During the upward movement of the plunger 52, piston ring 56 remains pressed against the lower side of the groove 57 by the compression spring 58 and by the working medium pressure in the buffer space 30. so that a good seal is obtained.

When a plunger 52 has passed the uppermost dead position and moves downwards, working medium in the compression space 51 is compressed and inlet valve 55 closes. When the working medium pressure in the compression space 51 is so high that the force in the upward direction exerted on the piston ring 56 by said working medium overcomes the force exerted thereon in the downward direction, piston ring 56 is pushed upwards and compression spring 58 is compressed. A gap then remains between the upper side of the piston ring 57 and the upper side of the groove 57. Working medium is then pressed from the compression space 51 along the piston ring 56 into the buffer space 30. Reduction of the working medium pressure in the working space of the engine again occurs by opening the cock 9.

What is claimed is:

1. In a hot-gas engine operable with a working medium and including a working space. the improvement in combination therewith of means for controlling the quantity by weight of working medium in the working space. comprising a storage container for working medium, a compressor with a low pressure inlet and a high-pressure outlet, first and second ducts communicating said storage container with said working space, and first and second controllable valve means respectively in said ducts. said first duct means communicating said storage container via said first valve with said compressor inlet, and communicating said compressor outlet with said working space, and said second duct means communicating said container via said second valve with said working space.

2. Apparatus according to claim 1 wherein said engine includes a buffer space, further comprising a check valve having an inlet communicating with said buffer space and outlet communicating with said sec ond duct between-said second valve and said working space.

3. Apparatus according to claim 1 wherein said engine includes a buffer space, and wherein said compressor is in said buffer space, and the apparatus further comprises a check valve having an inlet communicating with said buffer space and an outlet with said working space, and an additional check valve having an inlet communicating with said compressor outlet and an outlet communicating with said buffer space.

4. Apparatus according to claim 1 wherein said engine includes a buffer space, and wherein said compressor is in said buffer space, said apparatus further comprising a check valve having an inlet communicating with said buffer space and an outlet with said second duct between said second valve and said working space, and an additional check valve having an inlet communicating with said compressor outlet and an outlet with said buffer space. 

1. In a hot-gas engine operable with a working medium and including a working space, the improvement in combination therewith of means for controlling the quantity by weight of working medium in the working space, comprising a storage container for working medium, a compressor with a low pressure inlet and a high-pressure outlet, first and second ducts communicating said storage container with said working space, and first and second controllable valve means respectively in said ducts, said first duct means communicating said storage container via said first valve with said compressor inlet, and communicating said compressor outlet with said working space, and said second duct means communicating said container via said second valve with said working space.
 1. In a hot-gas engine operable with a working medium and including a working space, the improvement in combination therewith of means for controlling the quantity by weight of working medium in the working space, comprising a storage container for working medium, a compressor with a low pressure inlet and a high-pressure outlet, first and second ducts communicating said storage container with said working space, and first and second controllable valve means respectively in said ducts, said first duct means communicating said storage container via said first valve with said compressor inlet, and communicating said compressor outlet with said working space, and said second duct means communicating said container via said second valve with said working space.
 2. Apparatus according to claim 1 wherein said engine includes a buffer space, further comprising a check valve having an inlet communicating with said buffer space and outlet communicating with said second duct between said second valve and said working space.
 3. Apparatus according to claim 1 wherein said engine includes a buffer space, and wherein said compressor is in said buffer space, and the apparatus further comprises a check valve having an inlet communicating with said buffer space and an outlet with said working space, and an additional check valve having an inlet communicating with said compressor outlet and an outlet communicating with said buffer space. 